Catheter guide wires of a known type have an elongated wire shaft of a flexible material with a proximal and a distal end. In the distal end area, one or more radiopaque, sleeve-like markers are disposed on the wire shaft, which have essentially two functions. On one hand, the position of the guide wire tip must be easily visible on an x-ray monitor—for example by means of an elongated marker coil directly at the distal end of the guide wire—while the catheter is being applied. On the other hand, a length measurement of a stenosis to be treated can be performed on the X-ray monitor, for example, with the aid of multiple markers that are equidistantly spaced adjacent to the distal end.
Guide wires of this type are known in their fundamental design from a multitude of printed publications. U.S. Pat. No. 5,209,730 A, for example, shows a catheter guide wire that has an elongated wire shaft of a flexible material, namely high-strength stainless steel. On it, radiopaque markers are disposed adjacent to the distal end, which are formed by coiled spring elements—so-called “coils”—and which serve—as mentioned above—for measuring the length of stenoses.
U.S. Pat. No. 5,479,938 reveals a similar catheter guide wire on whose shaft radiopaque markers in the form of metal sleeves—also for measuring the length of stenoses—are disposed spaced progressively further apart as their distance from the distal end increases. They may be beveled at their front edges facing in the longitudinal direction of the wire.
Catheter guide wires of this type pose the problem that the wire, especially at its distal end, needs to be as flexible as possible on one hand in order to ensure the most atraumatic insertion of the wire into coronary vessels, and in the process a smooth passage through narrow points and bends in the vasculature being targeted; on the other hand, the markers that are used to identify the guide wire in the case of an X-ray monitoring during the performance of a PTCA, require a certain material volume in order to keep the achievable contrast in the X-ray image at a suitable level. The markers based on a helically wound wire coil that were mentioned at the beginning thus need be mounted on the largest possible winding core, which is diametrically opposed to the demand for the thinnest possible diameter of the wire shaft.
To solve this problem, the invention proposes that the marker or markers are disposed in each case on a core section that is widened in its diameter relative to the adjoining shaft sections of the wire shaft. In other words, a positioning surface that permits a larger diameter of the marker sleeve relative to the remaining wire shaft is provided, only at the locations where the marker is to be located. To maintain the flexibility of the guide wire, the sections that are located between the markers are implemented thinner. The thickened core sections do not cause any significant deterioration of the bending behavior of such guide wires since the flexibility in the regions of the markers is already restricted by this additional component. Additionally, the thickened core section renders the coils easier to solder and center.
According to preferred embodiments of the invention, the core sections transition on both sides in ramp-like annular shoulders in each case into the adjoining shaft section. This prevents sharp inner corners and edges that are difficult to manage from a production aspect given the small dimensions of such guide wires. This is true especially for the processing steps of grinding and polishing the wire. Sharp inner corners would eventually lead to an increased susceptibility of the wire shaft to notch breakage.
According to an additional preferred embodiment, provision is made for the marker, which is implemented as a wire coil, to be secured in each case on the core section by means of a solder bed. The solder bed tapers off at its two ends in a frusto-conical ramp in each case toward the adjoining shaft section and is adapted in this manner to the conical annular shoulder of the core sections. In this respect no interfering edges result on the product, especially after the grinding and polishing of such a guide wire with marker, which could cause injuries to the vessel wall—so-called “dissections”—while the wire is being inserted.
Additional preferred embodiments relate to the dimension ratios of the wire shaft and multiple markers. Of advantage in this case is especially the somewhat smaller outside diameter of the markers in comparison with the distal marker coils that customarily exist on such catheter wires.
This prevents a jolt-like onset of friction when the guide wire is shifted relative to the PTCA catheter. Additional characteristics, advantages and details of the invention will become apparent from the following description, in which an example embodiment will be explained in more detail based on the appended drawings.